Fire control intervalometer



July l J. B. WRIGHT ET AL .A FIRE CONTROL INTERVALOMETER Filed March 28,1968 IOP-gw h @Zan-uhm mmc James B.Wright Joy F. Honeycutt,

INVENTORS.

mowlw ATToRNEys United sees Patent o U.S. Cl. 317-80 5 Claims ABSTRACTOF THE DISCLOSURE A solid state controlled, electromechanicalintervalometer which furnishes a preselected number of output pulses ata predetermined rate in response to an input command. The intervalometerhas three `basic sections in its operation: (l) a control circuit, whichinitiates the vring and reset circuits and visually indicates thecondition of the device at all times, (2) an oscillator circuit, whichconsists of relays and contacts for furnishing preselected output pulsesand (3) a timing circuit, which consists of five individual timefunctions for the output pulses.

Dedicaory clause The invention described herein may be manufactured,used, and licensed by or for the Government for governmental purposeswithout the payment to us of any roy alty thereon.

Background of the invention This invention relates in general tocontrolled timing of pulses for an airborne fire control device, andmore particularly to an intervalometer for preselecting a number of ringpulses with controlled intervals for firing rocket pairs in ripple re.

Summary of the invention The present invention comprises means forfurnishing a preselected number of output pulses at a preselected ratein response to an input command. This operation controls the number ofrocket pairs tired when a fire cornmand button is pressed. Theintervalometer will automatically tire the number of preselected pairsof rockets in sequence and then shut-off until an operator releases andthen recloses the lire command button for another ripple of ring. Thecircuit can be preset to re l, 2, 3, 4, 6 or twenty-four rocket pairs orcan be stopped at anytime in the selected cycle by releasing the firecommand button. A digital counter coil keeps a running total of thenumber of rocket pairs red, allowing the aircraft operator to know thecondition of the intervalometer at all times. The intervalometer hasthree basic sections in its operation: (l) a control circuit, whichinitiates the ring and reset circuits and visually indicates thecondition of the device at all times, (2) an oscillator circuit, whichconsists of relays and contacts for furnishing preselected output pulsesand (3) a timing circuit, which consists of ve individual time functionsfor controlling the number of output pulses furnished for ring rocketmotor squibs.

It is an object of the present invention to provide a novel means ofcontrolling the ring rate and num-ber of rockets tired by a fire controlintervalometer.

It is another object of the present invention to provide automatictiring means for ring rockets in a number of preselected pairs.

It is a further object of the present invention to provide a means forliring all rockets in a bank sequentially or to terminate ring of therockets anytime in the cycle.

Other objects will be readily appreciated and the invention may bebetter understood by reference to the 3,453,496 Patented July 1, 1969ice Brief description of the drawing The figure is a schematic diagramof the intervalometer of the present invention.

Detailed description of the drawing Refer now to the figure for adescription of the circuit of the intervalometer. The intervalometer iscontained in two units. One unit is located in a rocket armament panel70fand the other unit is a stepping switch coil and its related contactslocated in step switch unit 80. The armament panel 70 containsoscillator and timing circuits and various indicators of the controlcircuit. The step switch unit contains stepping switch 90, steppingswitch coil 14 and its relay contacts along with arming relay coil 12.The condition of the intervalometer can Ibe visually observed on thefront of the rocket armament panel at all times by an operator. Locatedon the front of the rocket Iarmament panel is a counter (not shown) thatis actuated by counter coil 22 each time oscillator action fires arocket pair, a safe lamp DS4, an arm lamp DSS, a zero lamp DS6indicating the location of the stepping switch 90 in the zero position,and a `selector switch 30 that is manually set by an operator to tire aselected number of rocket pairs when fire command button 28 is pressed.Selector switch 30 can choose l, 2, 3, 4, 6 and twenty-four rocket pairsto be fired when the re command button is pressed. The counter indicatesthe number of ring pulses generated by the intervalometer, correspondingto the number of rocket pairs fired. Counter coil 22 is pulsed each timerelay contact 20a cycles due to action of oscillator coil 20. ResistorR14 provides transient suppression for the counter coil.

The circuit is shown in the safe position as denoted by switch 52 beingclosed on the safe contact thereof. Switch 52 is directly connected to apositive voltage source at terminal 10. Lead 60 by-passes switch 52 andfurnishes the positive voltage to one side of push-button 62 where apress-to-test check of lamps DS4, DSS and DS6 can be made in whichburned out lamp elements can be replaced before the intervalometer goesinto operation. When switch 52 is closed on the armed contact, armingrelay coil 12 is activated by connecting the positive voltage source atterminal 10` to ground 50, through arming relay coil 12. When armingrelay coil 12 is activated, relay contact 12a closes and relay Contact12b opens, respectively connecting positive voltage source at terminal10 to armed lamp DSS and disconnecting the positive voltage source fromsafe lamp DS4, thus lighting lamp DSS and turning lamp DS4 off. Thisgives the operator a visual indication of the intervalometer being in anarmed condition. With relay contact 12a closed, the positive voltagesource is available to the rocket ring circuits. The voltage isconnected to the anode of rectifier CR3 and to one side of relay contact20a. Relay contact 20a is controlled by oscillator relay coil 20, whichwill be discussed later.

A description of the control circuit, oscillator and timing or gatingcircuits will now be given` When re switch 28 is pressed, a positivevoltage source, present at terminal 10, is connected on one 4side offire relay coil 16 and timing relay coil 18. The other side of lirerelay coil 16 is connected to ground `50, thus energizing the tire relaycoil. Timing relay coil 18 will remain de-energized until SCRI is tiredby timing out of the timing circuit, through rectier CRS, or whenstepping switch reaches the zero position, indicating that all therocket pairs have been fired. With re relay coil 16 energized, relaycontacts 16a and 16C close, connecting the positive voltage present atterminal 10, through closed relay contact 12a,

rectifier CR3', closed relay contacts 16a, 18a and 20'b to ground Sthrough stepping -switch coil 14 and to a wiper arm of stepping switchy90 through closed relay contact 16C. When stepping switch coil 14 isenergized, stepping switch 90 cocks toward one of twenty-four sets ofstepping switch contacts that are connected to twentyfour rocket motorsquibs 92. With stepping switch coil 14 energized, switch interruptercontact 14a closes, energizing oscillator relay coil 20 from positivevoltage source through closed relay contact 12a, CR3, closed contacts16a, 18a and 14a. When oscillator relay coil 20 is energized, relaycontact b opens, de-energizing stepping switch coil 14. Stepping switch90 advances and interrupter contact 14a opens, de-energizing oscillatorrelay coil 20, completing one cycle of oscillation. This arrangementprovides maximum oif time in stepping switch coil 14 'and steppingswitch 90 duty cycle which aids in the accuracy of the number of rocketsfired. This is because the signal to stop firing must yarrive while thestepping switch coil is de-energized, since the stepping switch advanceson dropout of its coil rather than on pickup. The oscillator isfree-running as long as the re command exists, and the timing circuithas not fired, opening the positive voltage supply. The frequency ofoscillation is determined by the length of time that the dropout ofoscillator relay coil 20 is delayed. The oscillator supplies a 6 cycleper second pulse to the stepping switch coil and to the rocket motorsquibs 92. This time delay is determined by the oscillator relay coil 20in parallel with resistor R9 and capacitor C4 which are in parallel withresistor R16 and potentiometer R15. When voltage from the positivevoltage Source is applied on the hot side of the parallel network,oscillator coil 20 is energized. When the positive voltage source isremoved from the hot side of the parallel network by oscillator action,oscillator relay coil 20 is held energized for a short time due to thecharge stored on capacitor C4. Capacitor C4 will discharge throughresistor R9, oscillator relay coil 20, resistor R16 and potentiometerR15. Potentiometer R15 allows this discharge time to be trimmed in orderto adjust oscillator frequency.

The oscillator circuit consists of oscillator relay coil 20 and its setof contacts `and stepping switch coil 14 and its interrupter contacts.if the operator desires all twentyfour rocket pairs to be red, he canset the selector knob on the rocket armament panel to 24 (correspondingto the position of selector switch 30 as shown in the figure) and thusshorting the input to unijunction transistor Q1, allowing the oscillatorto oscillate at 6 cycles per second until the zero position of thestepping switch 90 contacts is reached. Capacitor CS and resistor R10form a differentiator which generates a positive pulse from terminal 10through cam operated contact 90a, closed when stepping switch 90 arrivesat the zero position. The positive pulse goes through rectier CR6 to iresilicon controlled rectifier SCR1, energizing timing relay coil 18 andopening relay contact 18a, stopping the oscillator. Diode CR2 provides adischarge path for capacitor C5. When light DS6 is lit, it indicates thelocation of the stepping switch wiper arm as being in the zero position.When the positive step input from the diierentiator is applied to thegate of SCR1, ring 'SCR1 into conduction, its anode voltage isessentially at ground potential, along with the side of timing relaycoil 18` opposite the positive voltage source. With timing relay coil 18activated, relay contact 18a opens the positive line to the oscillatorcircuit. Resistor R13 .and diode CRI compose a voltage regulator whichprevents noise on the aircraft voltage supply from falsely triggeringthe timing circuit off.

The timing circuit allows for selection of six different numbers ofrocket pairs, as desired, to be red on each ripple of tire. This isaccomplished by firing uni-junction transistor Q1 with the voltagestored on capacitor C2. Capacitor C2 and serially connected resistorsR7, R6, RS, R4 and R12 form RC time functions for operation of thetiming circuit. Potentiometer R11 is used as a trimmer to oiset resistortolerance variations. The six terminals of selector switch 30 are usedto connect the six individual time functions `at the input ofunijunction transistor Q1. Resistor R8, Zener diode CR4 and capacitor`C3 form a voltage regulator which provides a constant D-C voltagereference for the RC timers. Resistor R3 and normally closed contact 16bserve as a bleeder path to remove any stored charge from capacitor C2when fire switch 28 is released. Resistor R1 furnishes temperaturestabilization for transistor Q1. When unijunction transistor Q1 is red,a signal developed across resistor R2 is coupled to the gate of siliconcontrolled rectifier SCR1, through rectier CRS, -ring SCR1 andactivating timing relay coil 18 and opening relay contact 18a. CapacitorC1 is initially charged and dumps additional energy into the circuitwhen the unijunction transistor fires to insure a gating on of SCR1.Thus, when a time equal to the RC time constant selected by selectorswitch 30 has lapsed, the number of 6 cycles per second pulses furnishedby the oscillator has fired that many rocket pairs. An example is thatof firing 6 rocket pairs by moving selector switch 30 to terminal 6 and,thus, connecting resistors R7, R6, RS, R4, R11 and R12 in series withcapacitor C2. The time function of the serial connection of the aboveresistors and capacitor C2 is equal to one second, allowing 6 pulses to=be furnished by the oscillator to -re 6 rocket pairs. After SCR1 isfired, its anode voltage is essentially at ground potential, causingtiming relay coil 1,8 to energize. When timing relay coil 18 isenergized, relay contact 18a opens the positive line to the oscillatorand oscillation ceases.

A cycle of ripple re will now be explained taking a ripple of 6 rocketpairs to be iired as an example. An operator can press push-button 62for a press-to-test check to see that lights DS4, DSS, and DS6 are notburned out. When it is found that all bulbs are burning, switch 52 isswitched to it-s armed contact, energizing arming relay coil 12, closingrelay contact 12a and opening relay contact 12b. Arm lamp DSS will lightby a positive voltage applied thereto and to the anode of rectifier CR3.A selector knob on the front of the rocket armament panel is connectedto selector switch 30 and its wiper arm is positioned on terminal 6,representing a ripple of `6 rocket pairs to be tired. The intervalometeris now ready to control ripple firing of 6 rocket pairs when an operatorpresses re switch 28.

When fire switch 28 is pressed, lire relay coil 16 is immediatelyactivated by positive voltage source 10 being connected through the coilto ground 50, while timing relay coil 18 is not connected to ground andthus remains deactivated. With re relay coil 16 activated, relaycontacts 16a and 16C close and 16b opens. Relay contact 16C connectspositive voltage source 10 to a wiper arm of stepping switch 90. Relaycontact 16a connects positive voltage source 10 through rectifier CR3,contacts 16a, 18a and 20b to ground 50, through stepping switch coil 14.Stepping switch coil 14 is activated, closing relay contact 14a whichapplies positive voltage source 10 to one side of a parallel networkincluding oscillator coil 20 and resistor R9 and capacitor C4 inparallel with resistor R16 and potentiometer R15. Contacts 90a, 90b and90C are activated by a cam when stepping switch reaches a zero positionand the action resulting will be explained later. With positive voltagesource 10` connected to ground 50 through oscillator relay coil 20, theoscillator coil will be activated, thus closing relay contact 20a andopening relay contact 20b. When relay contact 20a closes, positivevoltage source 10 is applied to counter coil 22. When relay contact 20bopens, positive voltage source 10 is removed from stepping switch coil14, thus deactivating the stepping switch coil and opening relay Contact14a. With relay contact 14a opened, positive voltage source 10 isremoved from the parallel network including oscillator relay coil 20,and relay contacts 20a and 20b open and close again simultaneously. Whenpositive voltage source is removed from counter coil 22, one count isdigitally recorded and stepping switch coil 14 is activated to beginanother cycle of oscillation.

Each time stepping switch coil 14 is activated the wiper arm of steppingswitch 90 cocks and upon deactivation the wiper arm advances One of thetwenty-four rocket motor squibs 92 will fire on advance of the wiper armto the contact connected thereto. These oscillations and subsequentrocket motor squib firings will continue until a gating circuitactivates timing relay coil 18, and thus removes the positive voltagesource 10 from the oscillator circuit.

With oscillations of 6 pulses per second and 6 rocket motor squibsdesired to be fired, the oscillator circuit will need to ybe activatedfor one second. As stated above, selector switch wiper arm waspositioned on terminal 6 to obtain controlled firing of 6 rocket pairs.Positive voltage source 10 is connected to the timing function,consisting of resistors R8, R12, R11, R4, R5, R6 and R7 and capacitorC2, through rectifier CR3 and relay contacts 16a and 18a as long asrelay contacts 16a and 18a are closed. Only two occurrences willinterrupt this continuity. One is for the operator to release fireswitch 28 and deactivates fire relay coil 16 before the 1 second of timeelapses or for the 1 second of time to elapse and a charge at the inputof unijunction transistor Q1 to become large enough to fire theunijunction transistor. When the operator keeps fire switch 28 connectedfor the 1 second, or more, then relay contact 18a will open, removingpositive voltage source 10 from the oscillator circuit. A voltagedeveloped across resistor R2 is coupled to the gate of siliconcontrolled rectifier SCRI, through rectifier CRS, firing SCRl andactivating timing relay coil 18. Another means of firing siliconcontrolled rectifier SCRI is by a positive pulse connected to its gatethrough rectifier CR6 connected to the junction of resistor R10 andcapacitor C5, where a positive pulse is formed when contact 90a closes.

The intervalometer can -be reset to the stepping switch zero position atany time by placing switch 52 in the safe position and pressing resetswitch 26. Cam operated contacts 90a, 90b and 90e are as shown in FIGUREl when stepping switch 90 is in the zero position. However, whenresetting back to the zero position, contact 90C will be cl-osed andcontacts 90a and 90bv will be opened. When reset button 26 is closed, apositive voltage from terminal 10 will `be connected to one side ofstepping switch coil 14 through closed contacts 90e and 20b, thusactivating stepping switch coil 14 and closing relay contact 14a. Withrelay contact 14a closed, positive voltage from terminal 10 is appliedto one side of oscillator coil 20, through closed contacts 90e and 14a.Oscillator relay coil 20 will be activated and relay contact 20b opened,removing the positive voltage from stepping switch coil 14, thus openingrelay contact 14a. When relay contact 14a opens, the positive voltage isremoved from one side of oscillator coil 20, deactivating the oscillatorcoil and reclosing relay contact 20b, and thus applying the positivevoltage to one side of stepping switch coil 14 again. This cycle isrepeated with stepping switch 90 advancing on a set of contacts eachoscillation until the wiper arm moves to the zero position where a camwill close contacts 90a and 90b and will open contact 90C. Zero lamp DSGwill light, giving the operator an indication that stepping switch 90wiper arm is in the zero position.

The foregoing is considered as illustrative only of the principles ofthe invention. While a specific embodiment of the invention has beenshown and described, other embodiments may be obvious to one skilled inthe art, in light of this disclosure. The invention should be limited inscope only by the following claims.

We claim:

1. A fire control intervalometer comprising: an oscillator means; apower supply means, said oscillator means being free running with saidpower supply means connected thereto and generating a plurality ofevenly spaced output pulses; a multistage stepping switch circuit meanshaving a plurality of output contacts and a relay controlled input forsequential connection with said plurality of output contacts; aplurality of rocket motor squibs with inputs to said plurality of rocketmotor squibs being connected to said plurality of output contacts ofsaid stepping switch circuit means; a gating means, said gating meansconnected between said oscillator circuit and said multistage steppingswitch circuit means for selectively passing a limited number of saidplurality of output pulses from oscillator means to said relaycontrolled input to said multistage stepping switch circuit means; and acontrol circuit means comprising a firing and reset means and visualindicating means for indicati-ng the condition of Said fire controlintervalometer at all times, said firing means connecting said powersupply means to said oscillator means for generating said plurality ofevenly spaced output pulses that relay switch said multistage steppingswitch circuit means for supplying a plurality of sequential pulses fromsaid output contacts of said multistage stepping switch circuit means tosaid plurality of rocket motor squibs.

2. A fire control intervalometer as set forth in claim 1 wherein saidgating means comprises a plurality of time functions and a selectorswitch means having a plurality of fixed terminals and a movable wiperarm whereby said selector switch wiper arm is manually positionable oneach of said fixed terminals to selectively choose the value of each ofsaid time functions, said time functions being connected between saidpower supply means and ground for timing out said power supply meansfrom said oscillator means and stopping said plurality of output pulsesfrom said oscillator means to said multistage stepping switch and saidplurality of rocket motor squibs.

3. A fire control intervalometer as set forth in claim 2 wherein saidgating means further comprises a unijunction transistor having its inputconnected to said time functions.

4. A tire control intervalometer as set forth in claim 3 wherein each ofsaid time functions corresponds to one of said selector switch fixedterminals where an additional resistor is placed in series withresistor-capacitor time functions for extending the time of build up forthe input voltage to said unijunction transistor firing level.

5. A re control intervalometer as set forth in claim 4 wherein saidgating means further comprises a control diode for controlling a siliconcontrolled rectifier that in turn controls a timing relay coil and saidsilicon controlled rectifier lhaving a gate that is connected to anoutput of said unijunction transistor for gating said silicon controlledrectifier on an activating said timing relay coil said unijunctiontransistor fires thus opening a relay contact to said oscillator meansfrom said power source.

References Cited UNITED STATES PATENTS 3,311,788 3/1967 Paige 317-803,312,869 4/1967 Werner 317-80 3,316,451 4/1967 Silberman 317-803,133,231 5/1964 Faie et al 317-80 3,396,628 8/1968 Nash 89-1.814

VOLODYMYR Y. MAYEWSKY, Primary Examiner.

U.S. Cl. X.R.

